1. Field of the Invention
The present invention relates to a terminal electrode forming method for a chip-style electronic component and an apparatus therefor, and more particularly to a terminal electrode forming method for a chip-style electronic component and an apparatus therefor, capable of adapting to miniaturization of the chip-style electronic component, improving the quality of the terminal electrode and adaptable to mass production by executing conductive paste coating etc. while holding the chip-style electronic component by a film coated with an adhesive material.
2. Related Background Art
In general, the terminal electrode formation in a chip-style electronic component means forming a connecting electrode at an end of the chip-style electronic component by coating, drying and sintering paste containing silver, silver-palladium, copper etc. on such end portion, for the purpose of connection with an internal conductor or an internal electrode of the chip-style electronic component. The present invention describes a method for forming a terminal electrode on both ends of a chip-style electronic component such as a ceramic capacitor or a noise filter.
In the conventional terminal electrode forming method for the chip-style electronic component, the chip-style electronic components are held, as shown in FIG. 11, by forming holding holes 51 in silicone rubber 60 and inserting the chip-style electronic components 1, aligned by an insertion guide plate 52, into the holes 51 with inserting pins 53. Such holding method for the chip-style electronic components is however associated with the following drawbacks.
FIGS. 12 and 13 show a state in which the chip-style electronic components 1, inserted and held in the holding holes 51 shown in FIG. 11, are positioned downwards for conductive paste coating, and, in such state, the chip-style electronic components 1 are supported by the elasticity and friction of rubber 50. Thus, at the insertion, the chip-style electronic components are inserted by sliding into the holes 51 of the rubber 50, and, at the holding, they are supported by the elasticity of rubber 50 and the friction of the contact portions. Thus, the chip-style electronic component may not be properly placed at the desired position because sliding and friction, which are mutually contradicting factors, are involved and because of deformation of the rubber 50. Also the mutually contradicting relationship of sliding and friction cannot be controlled because of the miniaturization of the chip-style electronic component reduces the contact portion. Also as the holes are formed in the silicone rubber 50, it is necessary to pay attention to the abrasion of the holes 51 and to discard the rubber 50 after certain abrasion.
The feeding mechanism for feeding the chip-style electronic components into the holding holes 51 of silicone rubber 50 is associated with the following drawbacks. For feeding the chip-style electronic components, there is generated employed separation and alignment of the chip-style electronic components by sifting with the insertion guide plate 52 shown in FIG. 11. In this method, as the chip-style electronic components become smaller, the inserting pins 53 also become thinner, thus becoming insufficient in strength and precision. Also the mechanism (jig) becomes inevitably expensive because a high precision is required for the holes of the sifter and those of the holder, and also for the relative positional alignment thereof. In particular, such alignment work is extremely difficult.
Also the conveying mechanism for conveying the chip-style electronic components is associated with the following drawbacks.
The chip-style electronic components having been separated and aligned by the feeding mechanism are held and conveyed by the holes 51 of the silicone rubber 50 formed in the form of a plate or a belt. A plate-shaped holder is conveyed between the process steps either manually or by a robot arm. Manual conveying requires a high labor cost, while robot conveying requires a large and expensive equipment. Also a belt-shaped holder can reduce the labor cost and the floor space required for the equipment, but requires a highly precise conveying mechanism, which inevitably becomes complex and expensive because the alignment is difficult.
Furthermore, the coating surface of the chip-style electronic component has the following difficulties.
Prior to the coating with the conductive paste, the coating faces of the chip-style electronic components have to be aligned with a high precision. Without such alignment work, the dimension B, shown in FIG. 10, of a terminal electrode 2 formed on both ends of the chip-style electronic component 1, namely the length of the electrode in the longitudinal direction of the component, shows a significant fluctuation, and the terminal electrode may not be formed in the worst case.
On the other hand, the plate-shaped holder is suitable for mass production because of the large area thereof, but it is difficult to ensure planarity. Also the belt-shaped holder is formed with a smaller area for a smaller size of production, but it is also difficult to ensure the position because of the reasons explained in relation to the holding method.
Furthermore, the coating mechanism for the conductive paste is associated with the following difficulties.
A coating mechanism shown in FIG. 14A is to form a uniform conductive paste layer 52 on a flat surface a coating bed 60 by means of a squeegee 61, while a coating mechanism shown in FIG. 14B is to form a uniform conductive paste layer 62, by a squeegee 61, on the peripheral surface of a coating roller 66 which is immersed in a lower part thereof in a conductive paste reservoir 65. The terminal electrodes are formed by immersing the end portions of the supported chip-style electronic components in the uniform conductive paste layer 62 formed on such flat surface or on such peripheral surface of the roller.
In case of the plate-shaped holder, the end portions are immersed in the paste layer formed on a flat surface as shown in FIG. 14A. A large area is employed in this method because mass production is intended, and it is difficult to ensure the planarity in such large area.
Also in case of the belt-shaped holder, there is generally employed the coating roller mechanism shown in FIG. 14B, but it is difficult to ensure the precision of the center of the roller and the straightness of the cylindrical surface constituting the roller. Also there is required a high precise parallel relationship between the paste layer and the chip-style electronic components.
Furthermore, the following difficulties are involved in the drying the conductive paste applied on the chip-style electronic components.
The drying of the conductive paste is achieved in an oven using a heater of the electric resistance type, by radiated heat and atmospheric temperature (convection). In order to complete drying by evaporating solvent contained in the paste constituting the terminal electrode, there is required a long time under a high temperature (for example 60 seconds at 180xc2x0 C.). In order to withstand such high temperature, the conveying mechanism has to be given a heat-resistant property (for example metal belt or heat-resistant conveyor). Consequently the design of the conveying system is limited, and such system inevitably involves complex mechanisms and control with a high cost. Also there is required a large floor space for the equipment. Furthermore, even in case the heat-resistant arrangements are adopted, there still result a change in the conveying position resulting from the thermal dilatation.
Furthermore, a reversing operation executed for forming the terminal electrodes on both ends of the chip-style electronic component is associated with the following difficulties.
In order to form the terminal electrodes on both ends of the chip-style electronic components, it is necessary to position the chip-style electronic components, inserted into the holes 51 of the silicone rubber 50, by pushing them out to the opposite side with the inserting pins 53. In this operation, it is difficult to ensure exact positioning and secure operation because of the reasons explained in relation to the holding method.
Furthermore, the discharging of the chip-style electronic components after the formation of the terminal electrodes, is associated with the following difficulties.
The chip-style electronic components after the formation of the terminal electrodes are finally pushed out from the holes of the silicone rubber for example into a receiving box, but, for this purpose, there is again required a complex mechanism for secure discharge.
Thus, the drawbacks in the conventional terminal electrode forming method can be listed as follows:
1) The terminal electrodes cannot be formed precisely and stably on miniaturized chip-style electronic component;
2) Replacement of the kind of the chip-style electronic components to be processed is time-consuming;
3) There are required high costs for the equipment, consumables and replacement parts;
4) The electrode dimension fluctuates significantly since secure positioning (holding) is not achieved at the electrode forming operation;
5) The relative positional (parallel) relationship between the conductive paste layer and the chip holder is unstable, resulting in a fluctuation in the dimensional precision of the electrode;
6) In the conveying operation in the drying oven, the conveying mechanism exhibits dimensional change and a loss in the holding ability because of the heat; and
7) The long drying time requires a long drying oven, leading to a larger equipment.
In consideration of the foregoing, a first object of the present invention is to provide a terminal electrode forming method for a chip-style electronic component and an apparatus therefor, capable of adapted to the miniaturization of the chip-style electronic component and improving the quality of the terminal electrode.
A second object of the present invention is to provide a terminal electrode forming method for a chip-style electronic component and an apparatus therefor, capable of reducing the manufacturing cost of the component by simplifying the manufacturing apparatus and reducing the cost thereof, and also enabling mass production of the components of many kinds, by significantly reducing the preparation time required for changing the kind.
The above-mentioned objects can be attained, according to the present invention, by a terminal electrode forming method for a chip-style electronic component, comprising:
an arraying step of arraying chip-style electronic components on an arraying flat bed thereby achieving positioning of the chip-style electronic components and aligning the faces thereof;
an adhering step of lowering a first film coated with an adhesive material, together with an adhering top plate parallel to the arraying flat bed, in relative manner thereby adhering ends of the positioned and aligned chip-style electronic components to the adhesive; and
a coating step of lowering the aforementioned first film on which the chip-style electronic components are adhered together with a coating top plate relative to and parallel to a coating flat bed provided thereon with a conductive paste layer of a constant thickness thereby pressing the other ends of the chip-style electronic components to the coating flat bed.
The above-mentioned terminal electrode forming method for the chip-style electronic component may further comprises:
a drying step of drying the conductive paste coated on the other ends of the chip-style electronic components in the coating step; and
a reversing step of positioning, on a reversing bed, a second film coated with an adhesive material, lowering the aforementioned first film holding the chip-style electronic components after the drying step, together with a reversing top plate, in relative manner thereby adhering the ends, coated with the conductive paste, of the chip-style electronic components to the adhesive of the second film, then peeling off the first film together with the adhesive material thereof, and reversing the second film holding the chip-style electronic components.
There is preferably adopted a configuration in which the aforementioned film is formed as a tape, which is fed from a roll and wound on another roll to convey the chip-style electronic components supported by the adhesive material.
The aforementioned drying step is preferably achieved by concentrating far-infrared light to the portions, coated with the conductive paste, of the chip-style electronic components.
There is preferably adopted a configuration in which the aforementioned adhesive is a thermal foaming-release adhesive and the first film and the adhesive thereof are peeled off from the chip-style electronic components supported by the second by heating of the first film.
According to the present invention, there is also provided a terminal electrode forming apparatus for a chip-style electronic component, comprising:
a first tape running mechanism to run a first adhesive tape coated with an adhesive on a surface thereof;
a second tape running mechanism to run a second adhesive tape coated with an adhesive on a surface thereof;
an electronic component supplying unit to adhere ends of a group of chip-style electronic components in an arrayed state, on a surface, coated with the adhesive, of the first adhesive tape;
a first paste applying unit for applying conductive paste by pressing the other ends of a group of the chip-style electronic components, conveyed by running of the first adhesive tape, to a coating flat bed;
a first drying unit for drying the conductive paste applied on the other ends of a group of the chip-style electronic components;
a transfer unit for transferring a group of the chip-style electronic components, after passing the drying unit, from the first adhesive tape to the second adhesive tape thereby causing the second adhesive tape to support the end, coated with the conducted paste, of the chip-style electronic components;
a second paste applying unit for applying conductive paste by pressing the ends, not coated with the conductive paste, of a group of the chip-style electronic components, conveyed by running of the second adhesive tape, to a coating flat bed;
a second drying unit for drying the conductive paste applied on the ends of the chip-style electronic components; and
a discharge unit for peeling a group of the chip-style electronic components from the second adhesive tape.
In the aforementioned terminal electrode forming apparatus for the chip-style electronic component, the electronic component supply unit, the first paste applying unit and the first drying unit provided along the running path of the first adhesive tape and the second paste applying unit and the second drying unit provided along the running path of the second adhesive tape are preferably provided in a substantially same vertical plane and in two steps of different heights.
It is further preferred that the first adhesive tape receives adhesion of the chip-style electronic components supplied by the electronic component supply unit in a state where the surface coated with the adhesive is positioned downwards and transfers the chip-style electronic components to the first paste coating unit and the first drying unit in a state supporting the chip-style electronic components at the lower side, and that the second adhesive tape receives adhesion of the chip-style electronic components in the transfer unit in a state where the surface coated with the adhesive positioned downwards and transfers the chip-style electronic components to the second paste coating unit and the second drying unit in a state supporting the chip-style electronic components in a state supporting the chip-style electronic components at the lower side of the second adhesive tape.
It is preferred that the adhesives applied on the first and second adhesive tapes are thermal foaming-release adhesives and that the forming temperature is higher in the second adhesive tape than in the first adhesive tape.
The electronic component supply unit is preferably provided with an arraying block having a plurality of through holes for housing the chip-style electronic components and capable of arraying the chip-style electronic components in a standing state, a reference block having a flat surface for contacting the lower surface of the arraying block thereby aligning the lower end positions of the chip-style electronic components, and a dropper for dropping the chip-style electronic components into the through holes.
Furthermore, in dropping the chip-style electronic components into the through holes by the dropper, there is preferably provided a gap between the lower surface of the arraying block and the reference block in such a manner that the upper ends of the chip-style electronic components do not protrude from the upper surface of the arraying block.
The first and second tape running mechanisms are preferably provided with vacuum suction rollers for respectively driving the first and second adhesive tapes.
It is also preferred that each of the first and second paste applying units forms, on the coating flat bed, a conductive paste layer for dipping and a conductive paste layer for blotting or a conductive paste uncoated surface and is adapted to execute a first operation of dipping end of a group of the chip-style electronic components into the conductive paste layer for dipping and a second operation of contacting such ends with the conductive paste layer for blotting or the conductive paste uncoated surface thereby returning the excessive conductive paste to the coating flat bed by blotting.
It is also preferred that the transfer unit positions the first adhesive tape at the lower side with the adhesive coated surface thereof on which the chip-style electronic components are adhered upwards and also positions the second adhesive tape at the upper side with the adhesive coated surface thereof downwards, thereby supporting the chip-style electronic components between the first and second adhesive tapes positioned in parallel manner, and that the chip-style electronic components are supported by the second adhesive tape by dissipating the adhesive property of the first adhesive tape.
It is furthermore preferred that the running direction of the first adhesive tape from the electronic component supply unit to the first paste applying unit and the first drying unit and the running direction of the second adhesive tape from the transfer unit to the second paste applying unit and the second drying unit are mutually opposite.
The present invention is featured by a fact that the chip-style electronic components are held by the adhesive material, and this feature will be explained further in the following.
In holding the chip-style electronic components, it is important not to perturb the posture thereof.
Conventionally, in order not to perturb the posture of the held chip-style electronic components, the holding is achieved by insertion into rubber holes or by mechanical chucking, so as to withstand the vibrations resulting from the conveying operation or the operations of process steps and the external perturbation (external force) caused by impact. It is in fact possible to prevent change in the posture by pressing from left and right and from front and back so as to withstand the external perturbation.
However, with the progress in the miniaturization of the chip-style electronic components, it is found that the holding executed for the purpose of preventing the external perturbation may become a cause of generating an external perturbation in establising the precision. For example, the chip-style electronic component inserted into the rubber hole with a perturbed posture is coated obliquely when subjected to coating without correction of the posture, or a deficient dimension of the electrode is found because the chip-style electronic component once positioned moves again by the elasticity of rubber.
In the present invention, an entirely different approach is made to the aforementioned issue and any holding is eliminated. Such approach eliminates all the factors limiting the increase of precision and allows to realize highly precise positioning.
Such approach consists of a method of only adhering an end portion (end face) of the chip-style electronic component and not employing any other holding means. The chip-style electronic component adhered by the adhesive has to withstand impacts such as vibrations in the conveying operation, but complex mechanisms can be dispensed with if such impacts or vibrations can be withstood. In the miniaturized chip-style electronic component, with its small mass, the moment generated by the abrupt acceleration or impact is limited and does not exceed the adhesive force.
The adhesive material supporting the chip-style electronic component functions as a cushioning material therefor when a vibration is applied as an external perturbation.
The adhering method provides following functions:
holding the chip-style electronic component;
absorbing the fluctuation in the external dimension of the chip-style electronic component;
absorbing an abnormal shape in the chip-style electronic component;
memorizing the shape of the absorbed fluctuation or abnormal shape; and
peelability of the chip-style electronic component.
The adhesive material, showing jelly-like property, changes its shape under the application of an excessive displacement, and can maintain such changed shape though the recovery of the shape occurs by several per cent by elasticity. Thus the chip-style electronic component can be held and conveyed, maintaining the posture at the attaching by adhesion. Therefore, if the attaching (feeding of the component) is executed with a highly precise positioning, such precision can be maintained thereafter.
Such holding method is applicable not only to a chip-style electronic component with a single terminal at the terminal electrode but also to a chip-style electronic component with plural terminals at the terminal electrode.
Other objects of the present invention, and the features thereof, will become fully apparent from the following detailed description of the embodiments.